The present invention relates to vehicle air conditioning (A/C) systems, and more particularly to charging valves for such systems.
Conventionally air conditioning systems for vehicles have employed R12 or more recently R134a as the refrigerant. For some situations, however, it is advantageous to employ carbon dioxide (CO2), or CO2 with a co-fluid, as the refrigerant. One drawback, however, with employing a CO2 based refrigerant is that it operates in the A/C system at a significantly higher pressure and temperature.
Even at this higher pressure, the A/C system must still seal well enough that the refrigerant does not leak out. Conventional seals employed for the lower pressure A/C systems have generally proven to be inadequate to maintain adequate seals in the high pressure CO2 systems.
In particular, A/C systems in vehicles require one or more charging (service) valves, for testing, charging, discharging and evacuating the refrigerant from the system. These charging valves in a CO2 system must seal-in the high pressure refrigerant while preventing permeation, leakage and rapid decompression damage to seals. Also, the charging valve must be temperature resistant, so that it can maintain a good seal over a long period of time under a wide range of temperatures, including temperatures as high as 180 degrees Celsius that can be reached when operating a CO2 based A/C system. Further, the charging valve must immediately close and seal as the service tool is removed. Charging valves in the current relatively low pressure A/C systems have proven to be inadequate to meet all of these requirements.
Thus, it is desirable to have a charging valve for a vehicle A/C system that overcomes the drawbacks of the prior charging valves when operating in a high pressure CO2 system. In particular, it is desirable to have an A/C system with a charging valve that will seal under high pressure, avoiding permeation, leakage, and rapid decompression damage, as well as maintain the seal at various temperatures, and seal immediately as the service tool is removed.
In its embodiments, the present invention contemplates a service valve for an air conditioning system adapted to selectively connect pressurized refrigerant within a cavity of the air conditioning system to a service tool. The service valve includes a valve body defining a valve bore having a first end exposed to the cavity and a second end adapted for operatively engaging the service tool, with the bore including a dynamic valve seating surface. The service valve also includes a valve pin assembly, mounted and slidable within the valve bore between an open position and a closed position, with the valve pin assembly including a primary seal portion, and a secondary seal portion mounted to the primary seal portion, with the secondary seal portion being made of an elastomeric material that is substantially softer than the primary seal material, and with the primary and the secondary seal portions sealingly engagable to the dynamic valve seating surface when the valve pin assembly is in the closed position such that the primary seal portion contacts the dynamic valve seating surface closer to the pressurized refrigerant than the secondary seal portion.
An embodiment of the present invention provides a charging valve for a high pressure, CO2, vehicle A/C system that has a two part seal for maintaining an adequate seal under various conditions.
An embodiment of the present invention also provides a charging valve with an elastomeric O-ring seal that allows for intermediate sealing of the valve and a polymer or metal seal for providing long term sealing of the valve. The long term seal may be formed of a polyimide, such as Vespel, tin plated copper, or other similar materials.
An embodiment of the present invention also provides a seal mounted in a housing connected to the A/C system, where a single seal is employed to seal both a dynamic seal and static seal. The seal may be formed of a rubber coated steel.
An embodiment of the present invention also provides for an inverted pin valve having a pin-to-adapter seal, allowing a pin valve and a pin valve seat to be formed integrally. The pin valve seal also may be formed of a rubber coated steel, or a double seal arrangement.
An advantage of the present invention is that the charging valve seals against both permeation and leakage, in a high pressure A/C system under various temperature conditions.
Another advantage of the present invention is that the charging valve seals immediately as a service tool is removed, after charging or testing an A/C system.